1. Field of the Invention
The present invention relates to an engine start system for aircraft and more particularly to a bi-directional converter-start/generator.
2. Description of the Prior Art
Most of the aircraft in service today use hydromechanically driven or controlled 400 Hz power systems. The Auxiliary Power Unit (APU) is also used in case of emergency. At present, the APU is started by a DC motor and the aircraft main engine is started by an air turbine. Once the engine picks up ignition speed, the air turbine must shut off or else a dangerous condition exists. One alternative attractive approach to main engine starting is to utilize an AC electric start. Such an AC electric start must provide constant voltage-constant frequency as well as constant voltage-variable frequency.
Even an AC electric start system requires several components working together in conjunction to provide engine start capabilities to the aircraft main engine. Each of these components adds weight, expense and complexity to the aircraft. One such critical component is a small power inverter for the exciter field winding of the engine. It is an object of the present invention to reduce weight, expense and complexity by eliminating this power inverter.